In known wind turbines for generating electrical energy from wind energy, the generator with an electrical load, often an electric grid, is operated in a grid-parallel mode. During operation of the wind turbine, the electrical non-reactive power provided by the generator may vary according to the current wind speed. This results in a situation in which the grid voltage, for example at the infeed point, can also vary according to the current wind speed.
However, when the electrical power generated is delivered to an electric grid, for example a public power grid, fluctuations in the grid voltage may ensue as a consequence. In connected loads are to be operated reliably, however, such fluctuations are permissible only within very narrow limits.
Larger deviations from the reference value for the grid voltage in the supply grid, in particular the medium high voltage level, may be compensated, for example, by actuating switching devices such as stepping transformers, by actuating the latter when actual values exceed or fall short of predetermined threshold values. In this way, the grid voltage is kept substantially constant within predefined tolerance limits.